Context: Melanoma accounts for 1-3% of all malignancies. It is usually diagnosed as metastasis in the draining lymph nodes, that is inguinal lymph node. Due to paucity of cytological studies on melanoma in India, the present study was undertaken. AIM: To study the cytomorphology of malignant melanoma and to correlate the cytological diagnosis with histopathology and clinical details. Settings and Design: Sixteen cytomorphological features were studied and analysed from the cases diagnosed as melanoma on cytology with histopathological correlation. Materials and Methods: Thirty patients diagnosed with malignant melanoma on fine-needle aspiration cytology (FNAC) were studied over a period of 10 years and compared by histopathology. Papanicolaou (Pap)- and May Grunwald Giemsa (MGG)-stained smears were studied and analysed for the cytomorphological spectrum of melanoma. Results: Among the 30 patients studied, males were 19 and females were 11 (M:F:1.7:1) with a mean age of 49.3 years. The commonest primary site was foot followed by maxilla and thigh. The most common site for metastasis was inguinal lymph node. All 30 cases had histopathological correlation. Pigmented melanophages (83%) was the predominant feature followed by presence of melanin pigment (77%) and pseudo-inclusions (73%). Condensed chromatin was observed in the majority of the patients (53%). Smooth and irregular nuclear contours were seen in combination in 37% of the cases. A combination of nuclear placement, that is eccentric and central was observed as a predominant feature (53%). Spindle cell pattern was the predominant shape. Among cytoplasmic features, melanin granules and vacuoles were equally distributed (50%). Mixed pattern, that is singly scattered plasmacytoid cell pattern and cell clusters was the predominant cell architecture. Conclusion: A spectrum of cytomorphological features in correlation with clinical details leads to greater precision in diagnosis and helps to avoid pitfalls in diagnosing melanoma.

Keywords: Cytomorphology, fine-needle aspiration cytology, melanoma

How to cite this article:Radhika K, Prayaga A K, Sundaram C. A clinicopathologic study of malignant melanoma based on cytomorphology. Indian J Cancer 2016;53:199-203

Melanoma accounts for 1-3% of all malignancies. It has an increasing incidence worldwide. It is commonly seen in the lower extremities and metastasises to the draining lymph nodes. Other common primary sites are trunk/head and neck.[1] The most common sites of metastases include inguinal lymph node, lung, brain, liver, bone marrow and intestine. Many studies from abroad have shown the most consistent and useful features of melanoma on fine-needle aspiration cytology (FNAC) specimens.[2],[3] There are not many cytological studies describing the morphological spectrum of melanoma in India. Hence, this study was undertaken to make an attempt in describing the various cytomorphological features of melanoma.

» Materials and Methods

A total of 30 patients diagnosed as melanoma on FNAC studied over a period of 10 years, that is from 1999 to 2008 were included in the study. Data were retrieved from records of pathology. The eligibility criteria for patients included FNAC with histopathological correlation. Patients with no clinical data and without FNAC correlation were excluded from the study. The material included Papanicolaou (Pap)- and May Grunwald Giemsa (MGG)-stained smears, and special stains were done wherever required. FNAC was done using a 22- to 23-G needle. The majority of the cases on aspiration yielded a blackish pigment. Smears were fixed in isopropyl alcohol for Pap staining and air-dried smears were used for MGG staining. Masson Fontana staining was done for some of the suspected cases of melanoma. Immunomarkers such as HMB-45 and S-100 protein were used on smears with doubtful morphology, where the intracytoplasmic melanin pigment was not appreciable. A small biopsy material was used for histological examination. Sixteen cytomorphological features were studied and analysed on both Pap- and MGG-stained smears.

» Results

The total number of patients studied was 30 (n = 30). There were 19 males and 11 females, with a ratio of 1.7:1. Age ranged from 32 to 65 years, with a mean age of 49.3 years.

[Table 1] shows the site-wise distribution of the primary and metastatic melanoma. The most common site of involvement was the lower extremity (26), with the left side (14) more common than the right side (12). The lesion was seen in the maxilla, uveal tract (choroid) and index finger of the right upper limb in one patient each. Site was not mentioned for one patient. Among the secondary site of involvement, the inguinal lymph node was the most common, but was equally distributed between the right and left side in 11 patients each. Two patients (7%) had metastasis in the sub-mandibular lymph node and one patient showed axillary lymph node metastasis. Metastasis was reported in the liver, lung and abdomen in one patient (4%) each. Combined metastases were seen in a single patient (4%) involving the liver and gall bladder. One patient (4%) had metastatic melanoma in the lung, liver and pleural fluid.

Table 1: Site-wise distribution of the primary and metastatic melanoma

Mason Fontana staining was done to demonstrate the melanin pigment in a few cytology smears and on cell block as an adjuvant in ascertaining the cytological diagnosis.

Nuclear contours were divided into smooth, irregular and a combination of both. Combined nuclear contours were seen in 11 patients (37%), irregular nuclear contour in 8 patients (27%) and smooth nuclear contour in11 patients (37%). Nucleoli were present in only 21 patients (70%).

Nuclear placement was studied in three forms: Eccentrically placed, centrally placed and a combination of both. Eccentrically placed nuclei were seen in 6 patients (20%), centrally placed nuclei in 8 patients (27%) and a combination was seen in16 patients (53%).

Among cytoplasmic features melanin granules and vacuoles were present in 15 patients (50%) each with equal distribution.

The predominant cell architecture was mixed pattern in 21 patients (70%) comprising both singly scattered plasmacytoid cells [Figure 3] and cell clusters. Only single-cell pattern was seen in 8 patients (27%) and cell clusters in a single patient (3%).

Clusters of cells were again divided into small or large clusters, and absence of clusters. Small or large clusters accounted for 83%.

Cytological diagnosis in all 30 patients had a histopathologic correlation.

» Discussion

Melanoma is an aggressive malignancy. Although uncommon in India compared with the West, it has a growing prevalence. It has a spectrum of cytomorphological features.

The incidence of malignant melanoma varies in different parts of the world. Several studies have related the sun exposure habits of patients with melanoma and found evidence that they have increased light sensitivity. A history of painful or blistering sunburn during childhood or adolescents is sometimes established.[4]

The role of chronic sun exposure is more controversial according to Schreiber et al.[5]

As per Armstrong [6], both total accumulated exposure to sunlight and intermittent intense exposure increase the risk of developing malignant melanoma.

The subtropical state of Queensland in northern Australia has the highest incidence of melanoma in the world – 32 new cases annually per 100,000 of the population. The incidence in Scotland is 4.9 per 100,000; in Scandinavia it is 10 per 100,000; and in Arizona 27 per 100,000. There appears to have been a doubling in the incidence of melanoma in the last decade or so. Despite this alarming trend, prognosis has continued to improve because patients are presenting at an earlier stage with smaller and, therefore, potentially curable lesions.[7],[8],[9],[10]

The mortality of melanoma has risen less dramatically than incidence, likely due to earlier diagnosis. There is considerable geographic variation in the incidence of melanoma, related to exposure to sunlight and susceptibility of the population. Thus, global incidence is highest in the Australian tropics, but very low in most other tropical countries with their less susceptible populations.[11]

In India, there are no research studies available in the literature indicating the exact incidence of melanoma. However, the cause of the big difference in incidence of malignant melanoma in India compared with the West is understandable because of the wheatish/brown/black complexion.

Intestinal melanoma as a primary is very rare. It is usually seen as a metastasis of cutaneous, ocular or anal melanomas. Our study showed a metastatic melanoma in the gastrointestinal tract involving the anal canal. However, FNAC was not carried out. Melanoma of the sinonasal tract is rare, which has a wide range of cytological findings. Helsel et al.[12] reported a review of 22 primary and metastatic tumors. We have reported a single case arising in the maxillary sinus as a primary and metastasising the sub-mandibular lymph node. Grewal et al.[13] from India reported a single case of melanoma arising in the nasopharynx. Bianciotto et al.[14] in their study reported 20% uveal melanomas and the current study showed only one such case arising in the choroid of right eye. Kujala et al.[15] reported 85 patients with primary uveal melanoma. Biswas et al.[16] from India in their clinical and histopathological characteristics of uveal melanoma reported an incidence of 0.02%, with choroid being the predominant site. We observed 3% of uveal melanoma in our study, which shows that malignant melanoma of the uveal tract is rare in India. There are no large series on the uveal melanomas in the Asian Indian population.[14] Perry et al.[17] stated that lymph node aspirates of metastatic melanoma are usually composed of epithelioid cells with macro nucleoli or intra-nuclear invaginations. By contrast, our results show a predominant spindle cell shape. Piao et al.[18] in their study reported 62 patients exhibiting spindle cells as the predominant shape, which correlates with our findings. Presence of intracellular melanin in neoplastic cells is the gold standard to making a cytological diagnosis of melanoma.[3] However, routinely half of the cases may not show melanin. Such cases can have an additional help from ancillary techniques and previous surgical biopsy in arriving at the diagnosis. Typically melanoma is reactive for vimentin, S-100 protein, HMB-45, melan-A, tyrosinase and microphthalmia transcription factor. HMB-45 is a specific marker than S-100 protein.

Boutis et al.[19] reported a case of recurrent melanoma in literature which simulated clinically primary ovarian cancer. Our results did not show any case of melanoma metastasising the ovary.

Melanoma if it arises in soft parts is called clear-cell sarcoma. This is a rare and high-grade soft tissue sarcoma with high incidence rates of local recurrence and metastasis, and poor prognosis.[20] Caraway et al.[21] in their study of the cytology of malignant melanoma of soft parts gave an initial definitive diagnosis in two cases out of 13 fine-needle aspirates with the aid of immunocytochemical and ultrastructural studies. This indicates that the diagnosis can be made on FNAC alone if the cellularity is rich with morphological features indicative of melanoma. Clear-cell sarcoma (malignant melanoma of soft parts) was diagnosed on FNAC by Salem Shabb et al.[22] in 2003 from Lebanon, since there was no diagnostic dilemma in view of the abundant melanin. This article emphasizes that presence of melanin pigment in cytology smears acts as a diagnostic tool in identifying melanoma. Melanoma is also reported in rare sites like the vagina [23] as primary and as metastatic lesions in the parotid gland [24] and breast [25].

Yang et al.[27] stated that alteration of CXC chemokine genes may confer susceptibility to melanoma. These kind of genes need to be evaluated in less susceptible countries like India too.

Current therapeutic regimens attempt to eliminate all malignant cells of a melanoma lesion. But, melanoma is still maintained by a subset of cancer cells, which express CD20. Schiaak et al.[28] attempted removal of these cells by lesional injections of the anti-CD20 therapeutic antibody rituximab and concomitant dacarbazine treatment.

Nevus, malignant fibrous histiocytoma, scar, dermatofibroma, sclerotic dermatofibrosarcoma protuberans and leiomyosarcoma are the differential diagnoses that need to be considered during the diagnosis of melanoma.[1] Benign lesions can be differentiated from melanoma based on the absence of cytological features of malignancy. Leiomyosarcoma exhibits classical cigar-shaped nuclei in addition to nuclear pleomorphism and hyper-chromasia. In difficult cases, one can always take the help of ancillary technique, that is immunocytochemistry with bcl2.

In the literature there are not many cases of melanoma reported from India. This indicates that melanoma is relatively uncommon in India compared with the West.

» Conclusion

The lower extremity is the most common site for melanoma. Primary melanoma is rare. Metastatic melanoma is usually seen in the inguinal lymph node. Findings from the present study emphasize that a full awareness of the spectrum of morphological presentations of melanoma in addition to clinical history gives a greater precision in diagnosis and one can avoid the pitfalls in the diagnosis of melanoma.

Melanoma has variable cytomorphology. A high index of suspicion is necessary especially in low-prevalence areas like India.